1. Field of the Invention
The present invention relates to the field of displaying technology, and in particular to a low temperature poly-silicon thin-film transistor and a manufacturing method thereof.
2. The Related Arts
With the development of the displaying technology, flat panel displays, which have various advantages, such as high image quality, low power consumption, thin device body, and wide applications, have been widely used in various electronic consumer electronic products, such as mobile phones, televisions, personal digital assistants (PDAs), digital cameras, notebook computers, and desktop computers, and become the main stream of the display devices.
Active matrix (AM) flat panel displays are one of the most commonly used display device today. The active matrix flat panel display device includes a thin-film transistor to control input of a data signal in order to the control the displaying of an image.
Currently, the displaying technology is under fast development toward high definition. For example, the definition of a mobile phone has also reach a level as high as 1080P (1080×1920) and that of a television reaches even a higher level of 4K (4096×2160). With the increasingly heightening of definition, the driving power of the TFT device must be enhanced. Thus, a low temperature poly-silicon (LTPS) TFT, which possesses advantages high definition, fast response speed, high brightness, and high aperture ratio, is attracting increasing attention. To suit the need of driving power for high definition display devices, open state currents of a pixel zone and a driving zone of the display device must be increased and the way to increase the open state currents is to increase the width-to-length ratio of a channel of the TFT device. Specifically, the relationship between the open state current ID and the width-to-length ratio, W/T, of the TFT device is defined by the following equations: ID=(W/T)μCOX(VG−VT)VD for linear area; and ID=(1/2)(W/T)μCOX(VG−VT)2 for saturation area. It can be found from the above equations, for both linear area and saturation area, there are two ways to increase the open state currents, one being increasing the channel width W. However, with the increase of the channel width W, the aperture ratio of the display device is decreased thereby reducing the design flexibility of a panel. The second way is to shorten the channel length L. However, excessively shortened channel length L will increase the risk of breaking through of the channel. Consequently, the range of variability of the channel length L is limited.